Apparatuses for medical diagnostic measurement of physical conditions of animate subjects, such as human subjects or veterinary subjects, are often too bulky and too inefficient in their power consumption to be convenient for use. These limitations are especially disadvantageous when the desired use for such a diagnostic device is as a monitor for a condition associated with the subject. Such diagnostic devices would benefit from improved high speed communications among individual components within products or among products.
It is known, for example, that light absorption in tissue can be used to monitor changes in blood oxygenation and hematocrit (concentration of red blood cells). Generally, a light source, such as a laser, is used to illuminate the tissue being tested and resultant light is measured to identify a particular physical condition. Resultant light may be, for example, refracted light transmitted from one side of tissue through the tissue and received at an opposing side of the tissue. Resultant light may also include scattered reflected light that is detected on the same side of the tissue at which illumination is being effected.
Prior art apparatuses that employ such technology for medical or veterinary diagnostics, or other measurement of physical conditions of animate subjects, include several discrete devices, such as a laser, a light detector communications devices, data processing devices, and other devices. The cumbersome packaging that is necessitated by the employment of such discrete devices, and the necessary interconnecting wires, optic fibers, I/O (input/output) devices and other sundry components have been a barrier to widespread use of such devices, a barrier founded in high cost and inconvenience. The resultant bulky packaging for such discrete component products has particularly been a barrier to products that are easy enough to use and unobtrusive enough to employ to encourage use of the products as a xe2x80x9cwearablexe2x80x9d item for convenient continuous monitoring of an animate subject. Such wearable objects could include, for example, jewelry or articles of clothing.
Such prior art devices implemented in discrete components require interfaces such as high speed buses, I/O (input/output) interfaces for optical links or high speed RF (radio frequency) links, or other interface structures. Integration of the several devices that comprise a product into a unitary structure eliminates the need for some of the interfaces required for signal hand off, buffering and other functions that must be accomplished in a multi-element product. Prior art fabrication techniques available for producing unitary structures involving various semiconductor materials have proven prohibitively costly and space-inefficient to yield significant improvements by unifying structures.
A monolithic structure that achieves device unitary structure at the fabrication level reduces the need for individual I/O interfaces for each module transition, and thereby eliminates the need for on-chip xe2x80x9creal estatexe2x80x9d to accommodate such I/O interfaces. Other advantages realized by such a cost-efficient unitary fabrication ability include a significant reduction in size, an increase in operating speed, a reduction of electromagnetic noise and radiation emanations, an increase in performance reliability, a reduction in cost of manufacture and lower operating power requirements with an attendant lower cost of operation.
A capability for truly unitary fabrication employing a variety of semiconductor manufacturing technologies provides opportunities to produce multi-technology unitary structures that meet a wide variety of needs. For example, unitary structures may be fabricated to satisfy a wide variety of communication standards, such as cellular telephone standards, personal communication system (PCS) standards, xe2x80x9cBluetoothxe2x80x9d communication standards, and other industry-wide standards. Such compact construction capabilities permit manufacture of medical diagnostic products that are convenient to use, have long battery life, generate less radiation and electromagnetic noise, perform continuously, are lower in cost, and communicate test results reliably and cheaply, among other benefits.
Such advantages are particularly valuable in the manufacture of medical diagnostic and monitoring devices. Physical conditions such as heart rate, temperature, blood pressure, hematocrit (concentration of red blood cells), and other conditions may be continuously monitored or checked on command with convenient compact nonintrusive devices. Such devices may be fashioned to periodically sample, or check, a particular physical condition, compare a test result with a predetermined threshold or other criterion, and notify a remote user when the threshold or other criterion is met or exceeded. Such monitor equipment may be made compact enough to be integrally included into watches, jewelry, or other wearable items, including articles of clothing.
There is a need for a compact diagnostic monitoring device manifested in a cost-effective power-efficient integrated unitary structure, especially including a communication capability. Communications may be effected by any of various media: optic coupling, radio frequency coupling, sonic coupling, inductive coupling, capacitive coupling, magnetic coupling, or other communication media.
This invention relates generally to semiconductor structures and devices for medical diagnostic devices, including monitoring devices. This invention more specifically relates to compound semiconductor structures and devices and to the fabrication and use of semiconductor structures, devices, and integrated circuits that include a monocrystalline compound semiconductor material.
The preferred embodiment of the present invention is an apparatus for measuring at least one selected physical condition of an animate subject. The apparatus comprises: (a) a light source; (b) a light receiver; the light receiver receives resultant light from the light source via the subject; and (c) an information processor connected with at least the light receiver. The processor receives indication of the resultant light from the light receiver and evaluates the indication to effect the measuring. The processor is implemented in a unitary structure with at least one of the light source and the light detector. The unitary structure is borne upon a single silicon substrate. The apparatus may further comprise at least one first interface element coupled with the processor and with at least the light receiver. The first interface element facilitates communication with the processor. The first interface element is implemented in the unitary structure. The apparatus may even further comprise at least one second interface element coupled with the processor. The second interface element includes communication means for conveying messages to loci remote from the apparatus. The second interface element is implemented in the unitary structure.
The method of the present invention comprises the steps of: (a) providing a light source for illuminating the subject; (b) providing a light receiver for receiving resultant light from the subject; (c) providing an information processor connected with at least the light receiver for receiving indication of the resultant light from the light receiver; and (d) evaluating the indication to effect the measuring. The processor is implemented in a unitary structure with at least one of the light source and the light detector. The unitary structure is borne upon a single silicon substrate.
The unitary structure is comprised of a monolithic structure. At least a first portion of the monolithic structure is implemented in silicon, and at least a second portion of the monolithic structure is implemented in at least one compound semiconductor material.
The vast majority of semiconductor discrete devices and integrated circuits employed for medical diagnostic applications, including hematological and other measurements of physical conditions of animate subjects, such as humans, are fabricated from silicon, at least in part because of the availability of inexpensive, high quality monocrystalline silicon substrates. Other semiconductor materials, such as the so called compound semiconductor materials, have physical attributes, including wider bandgap and/or higher mobility than silicon, or direct band gaps that makes these materials advantageous for certain types of semiconductor devices. Unfortunately, compound semiconductor materials are generally much more expensive than silicon and are not available in large wafers as is silicon. Gallium arsenide (GaAs), the most readily available compound semiconductor material, is available in wafers only up to about 150 millimeters (mm) in diameter. In contrast, silicon wafers are available up to about 300 mm and are widely available at 200 mm. The 150 mm GaAs wafers are many times more expensive than are their silicon counterparts. Wafers of other compound semiconductor materials are even less available and are more expensive than GaAs.
Because of the desirable characteristics of compound semiconductor materials, and because of their present generally high cost and low availability in bulk form, for many years attempts have been made to grow thin films of the compound semiconductor materials on a foreign substrate. To achieve optimal characteristics of the compound semiconductor material, however, a monocrystalline film of high crystalline quality is desired. Attempts have been made, for example, to grow layers of a monocrystalline compound semiconductor material on germanium, silicon, and various insulators. These attempts have generally been unsuccessful because lattice mismatches between the host crystal and the grown crystal have caused the resulting thin film of compound semiconductor material to be of low crystalline quality.
If a large area thin film of high quality monocrystalline compound semiconductor material was available at low cost, a variety of semiconductor devices could advantageously be fabricated in that film at a low cost compared to the cost of fabricating such devices on a bulk wafer of compound semiconductor material or in an epitaxial film of such material on a bulk wafer of compound semiconductor material.
In addition, if a thin film of high quality monocrystalline compound semiconductor material could be realized on a bulk wafer such as a silicon wafer, an integrated device structure could be achieved that took advantage of the best properties of both the silicon and the compound semiconductor material.
Accordingly, a need exists for a semiconductor structure that provides a high quality monocrystalline compound semiconductor film over another monocrystalline material and for a process for making such a structure.